Selenium, Fluorine, and Arsenic in Surficial Materials of the Conterminous

Selenium, Fluorine, and Arsenic in Surfic"ial Materials of the Conterminous United States

By Hansford T. Shacklette, Josephine G. Boerngen, and John R. Keith


Washingto(l 1974 United States Department of the Interior ROGERS C. B. MORTON, Secretary

Geological Survey V. E. McKelvey, Director

Free on application to the U.S. Geological Survey, National Center, Reston, Va. 22092 CONTENTS

Page Abstract ...... 1 Fluorine-Continued Introduction ...... 1 Results of analyses ...... 6 Selenium ...... 2 Discussion ...... 6 Analytical method ...... 2 Arsenic ...... 10 Results of analyses ...... 2 Analytical method ...... 10 Discussion ...... 2 Results of analyses ...... 10 Fluorine ...... 3 Discussion ...... 10 Analytical method ...... 3 References cited ...... 11



FIGURE 1. Map showing selenium concentrations in surficial materials of the conterminous United States ...... 4 2. Map showing physiographic regions of the conterminous United States ...... 6 3. Map showing fluorine concentrations in surficial materials of the conterminous United States ...... 8 4. Map showing arsenic concentrations in surficial materials of the conterminous United States ...... 12


TABLE~ 1-3 · Concentrations of elements in samples of and other surficial materials from the conterminous United States: Page 1. Selenium...... 2 2. Fluorine ...... 6 3. Arsenic ...... 10


Selenium, Fluorine, and Arsenic in Surficial Materials of the Conterminous United States

By Hansford T. Shacklette, Josephine G. Boerngen, and John R. Keith

ABSTRACT trations were determined by J. W. Budinsky, B. A. Concentrations of selenium, fluorine, and arsenic in 912, 911, McCall, and Roosevelt Moore. and 910 samples, respectively, of soils and other regoliths from We measured the precision of the analytical sites approximately 50 miles (80 km) apart throughout the methods used for these elements by analyzing 48 United States are represented on maps by symbols showing five randomly selected samples in duplicate. The 48 ranges of values. Histograms of the concentrations of these duplicates were randomly interspersed among the elements are also given. The geometric-mean concentrations (ppm) in the samples, grouped by area, are as follows: other 912 samples and were unknown to the analysts. The precision of each method was es­ Selenium- Entire United States, 0.31; Western United States, timated by 0.25; and Eastern United States, 0.39. 48 ~(log x ·-logy ·) 2 Fluorine- Entire United States, 180; Western United States, . 1 £ t 250; and Eastern United States, 115. sJ= z= 0.00040, Arsenic- Entire United States, 5.8; Western United States, 96 6.1; and Eastern United States, 5.4. where s& is the precisiOn, and xi and Yi are, respectively, the determinations of each element INTRODUCTION for the ith sample and its corresponding duplicate. The concentrations of 38 elements in samples of The analytical reproducibility, as as the soils and other regoliths from sites about 50 miles logarithmic variance, for each of the three (80 km) apart on travel routes throughout the con­ elements is given later in this report. terminous United States were given by Shacklette, Analytical values for the three elements were Hamilton, Boerngen, and Bowles (1971), transformed to a logarithmic form because the Shacklette, Boerngen, and Turner (1971), and frequency distributions are more nearly sym­ Shacklette, Boerngen, Cahill, and Rahill (1973). metrical on a logarithmic scale than on an arith­ After these reports were prepared, analytical metic scale. The best measure of central tendency methods became available for determining in a lognormal distribution is the geometric mean, selenium, fluorine, and arsenic in surficial which is the antilogarithm of the mean logarithm. materials in concentrations as low as 0.1 ppm (part The most convenient measure of variation is the per million), 10 ppm, and 1 ppm, respectively. geometric deviation, which is the antilogarithm of The samples were collected and prepared for the standard deviation of the logarithms. analysis in the same manner as reported earlier Estimates of the arithmetic mean (tables 1-3) were (Shacklette, Hamilton, and others, 1971) and were derived by the use of Sichel's (1952) technique. analyzed in sequence that was completely random These methods of statistical evaluation are the with respect to sampling locality. Selenium con­ same as those used for evaluating other elements centrations were determined by J. S. Wahlberg in the samples, as reported by Shacklette, and M. W. Solt, and fluorine and arsenic concen- Hamilton, Boerngen, and Bowles (1971).

1 Although most of the samples studied were west of the 97th meridian, are given in table 1. collected along roads, the specific sampling sites Figure 1 shows the distribution of the sample sites were selected to obtain surficial materials that throughout the conterminous United States and were as representative as possible of their natural the selenium concentrations of the samples, ex­ condition. Some samples, of necessity, were pressed in terms of five geometric ranges of con­ collected in cultivated fields; the degree of con­ centration. tamination, if any, of these samples or of a few samples collected near road shoulders cannot be TABLE !.-Concentrations of selenium, in pa-rts per million, in sa.mples ofsoils and other surficial materials from the conter­ evaluated from the data at hand. Most surficial minous United States materials analyzed were sampled at a depth of [Number of samples is given in parentheses after area] about 8 inches (20 em). We believe that soils and ...... other regoliths from this depth are influenced very ·;:::: = ·E·~ e... -; Area ~ 8 -~ little by the surficial contamination associated ~ ~ 0 .., .s g e ..,., = C,!) ~8 with roadways. ~ C,!)

Many geologists and other workers of the U.S. Entire conterminous Geological Survey assisted in this study by collect­ United States (912) 0.1-4.32 0.31 2.42 0.45 Western United States, ing samples along travel routes to their own field­ west of the 97th meridian (492) ...... 1-4.32 .25 2.53 .38 study areas. This assistance, and that of computer Eastern United States, east of the 97th specialists, was acknowledged in the earlier meridian (420) ...... 1-3.88 .39 2.17 .52 reports of this sampling program (Shacklette, Hamilton, and others, 1971; Shacklette, Boerngen, 'Estimated by method of Sichel (1952). and Turner, 1971.)

SELENIUM DISCUSSION ANALYTICAL METHOD The concentrations of selenium in natural Selenium concentrations in the samples were de­ materials, including soils, have been extensively termined by a chemical-X-ray fluorescence method. investigated because of the long-known of A 2-g (gram) sample is fused with 15-g sodium this element to domestic animals and man and, carbonate and 5-g sodium peroxide. The fusion more recently, because the essentiality of selenium cake is then dissolved in 200 ml (milliliters) of in animal metabolism has been established. The water, and the solution is filtered. The filtrate is dual metabolic role of this element was discussed acidified, a tellurium carrier added, and the by Frost (1972). The relationships of selenium selenium along with the carrier is precipitated by chemistry and agricultural practices were dis­ an iodide sulfite reduction reaction. The cussed in an handbook by Anderson, precipitate of selenium and tellurium is collected Lakin, Beeson, Smith, and Thacker (1961), and on a filter disk and dried, and the quantity of more than 200 literature references to the subject selenium is then determined by X-ray were given. More recently, reports were published fluorescence. of .selenium accumulation in soils, plants, and The logarithmic variance of the analytical animals to levels that are toxic (Lakin, 1972) and cf method was measured as 0.042729. This means effects of selenium deficiency in soils on animal that the analyses are reproducible within a factor health (Muth and Allaway, 1963; Allaway, 1969; of 1.61, computed as the antilog of sa at the 68- and Oldfield, 1972). Selenium is generally con­ percent level of confidence, or within a factor of sidered to be nonessential in plant metabolism. 2.59, computed as the square of the antilog sa at Low concentrations of this element, however, have the 95-percent level. The logarithmic variance of been shown to stimulate plant growth (Ganje, selenium measured in all 912 samples is 0.1476, in­ 1966, p. 394). dicating that the analytical-error variance con­ Lakin (1961, p. 27) outlined the sources of tributed less than 29 percent to the total variance selenium in soils .as follows: "The selenium in soils in the data. may be derived (1) from parent material weathered from the underlying rock; (2) from RESULTS OF ANALYSES wind- or water-deposited seleniferous materials; (3) Statistics for the selenium concentration of all from ground or surface water, by precipitation; (4) samples, as well as of samples from both east and from volcanic emanations brought down by rain;

2 and (5) from sediments derived from mining absorbed by native nonseleniferous plants and by operations. All these types are known." cultivated crop plants. These selenium­ In general, seleniferous soils of dry regions are concentrating plants were designated "selenium­ alkaline, contain free calcium carbonate, and may converter" plants by Beeson (1961, p. 37). support seleniferous plants that are toxic to The difference in geometric-mean concen­ livestock. In the United States most soils of this trations of selenium in samples of surficial type are west of the 97th meridian. Soils of more materials from the Eastern and Western United humid regions are generally acidic and, even if States, as given in table 1, is statistically signifi­ seleniferous, are not known to support seleniferous cant at the 99-percent confidence level. Some plants. The differences in toxic properties of patterns in the distribution of selenium concen­ selenium in arid and humid regions were explained trations are apparent at a smaller scale. The by Lakin (1961, p. 30): "Although many -factors generally low concentrations in samples from the govern the selenium uptake by plants, a partial northern part of the Cordilleran Mountain region measure of selenium's availability to plants is its (fig. 2) and the high values in the northwestern solubility in water. Toxic soils contain water­ part of the Great Plains region are thought to soluble selenium; the others do not. From the reflect concentrations in the bedrock that largely physical chemistry of selenium one finds that it constituted the soil-parent material. The generally may be oxidized to selenates in a moist alkaline en­ low concentrations in samples from the vironment; the formation of selenates in an southeastern part of the Atlantic Coastal Plain environment is not likely. One may conclude that region and the high values in samples from the in regions of low rainfall, the alkaline seleniferous deltas of major streams in the central part of the soils will contain CaSe04, which is soluble in water Gulf of coast probably reflect the chemical and available to plants; in regions of high rainfall, composition of the sediments from which the soils the acid seleniferous soils will not contain selenic were formed. The absence of a clearly defined acid, which, if formed, would be leached out of the pattern of high values that correspond to the so­ soil." In addition to water-soluble selenates, water­ called seleniferous soils of the northern and soluble organic selenium also occurs in some soils, western parts of the Great Plains region and the and micro-organisms are thought to be important adjacent parts of the Rocky Mountains is probably in its formation (Lakin, 1972, p. 183-184). a reflection of the fact that total, rather than Goldschmidt (1954, p. 532) stated that the abun­ available, concentrations of selenium were deter­ dance of selenium in magmatic rocks of the earth's mined in this study; or, the absence may be due to crust is 0.09 ppm. This element is greatly enriched insufficient sampling , or it may reflect in certain geologic materials, such as both factors. Nevertheless, the range in reported rocks that may contain as much as 55 ppm and selenium values and the means that were com­ black shales that may contain up to 675 ppm puted are believed to be useful indicators of the (Lakin,1972,p.181). Vinogradov(1959,p.183)gave concentrations of total selenium than can be ex­ the selenium content of soils as 0.01 ppm, and pected to occur in surficial materials of the conter­ Swaine (1955, p. 91) stated that most soils contain minous United States, although these values are 0.1-2 ppm selenium. In discussing geochemical higher than those given for soils by Hawkes and prospecting by analyzing soils for selenium, Webb (1962, p. 372) and Vinogradov (1959, p. 183). Hawkes and Webb (1962, p. 372) stated that, because of the association of this element with FLUORINE epigenetic , the abundance of this element may be used as an indication of base- ANALYTICAL METHOD deposits. Fluorine was determined potentiometrically by Studies of the distribution of selenium-indicator using a fluoride specific-ion electrode, according to plants have led to the discovery of selenium-rich the procedure described by Ingram (1970). We deposits in the Western United States found the logarithmic variance of the analytical (Cannon, 1960). Some of the indicator plants con­ method to be 0.11. This means that the analyses centrate selenium in their tissues by extracting it are reproducible within a factor of 2.17, computed from selenium that are relatively in­ as the antilog of sa at the 68-percent level of con­ soluble; when the plants die and decompose, the fidence, or within a factor of 4.72, computed as the selenium is released in a chemical form that can be square of the antilog of sn at the 95-percent level.

3 t

[B!J!J.ms u! suon-e.r~uaauoa wn!uaras-·r :1111nm~

oll NOilliW ll:ld S..i.IIVd NI'Wn1N313S 1\ ·WN---coOCOOOOQO b~·=·~~~~·WN~~~~ cn ...... No-~cac.n- ~' oVl ~ ~ I v ', I ee o ~ I o9l J. I 001 vee e e e e .,.' ;6"-. - I ~-....,./- ', I Ul I l I 1 I I e e v 1e1el V IOLo!H ev \ •w ~ ~ ~ ;; o8l eoe e v'' S31dWVS 1\f!Ol :JO e e e eev e v :\. 39\f1N3:1113d ON\f 108WAS e v v I e o v f> v e ;eT!f),-~~--JTj):::-o-1 ...... e e e e v o eP evv o v 0 ...... _ oO£ ~ ' e oh 0 ...... "'-""vw-.,9 v f) v e (.) e IV 0 ' -.."- e b v I e ...... v v v e e~ v • v e. e e v f • o v .L I .. • I v v v ~ v o e 0 o o~ --~ ol£ v o v e v t-' v v 0 / o , () 0 V t ~ I t) ~v• e~ v~,.I {) o 1 v e e e v 1 v ' c v ~ • • .... _ --- e v• vI v e e -e-e--o-o--e--r~~-!_ v v • e I e v ,\c o o e ~a. oV£ • e e e ----'_ 0 ee 1 OJ ' e e e e e e v .Le e ---~.2_ r ..... o ' c , e • / ----- ~ Je \ e e • 1 "lJ-~ o e. e 'e o 1 0 ' e I o9£ • e e e I e v / • / O\ .. ------'-e e e e e e e o. v ' --l e I I \ ::-'!• e e e ., " e., 1 e 1 ., ., ~ e \ e e v Oev v ot'>. • ' e!...~e o•~ ~ o8£ \ e o v I:>L Q / , o e e T------~ v e - __e='eev 0 ~ 0 ovoo~ e) .,_ o 0 p" e e " e I e o" e o I ee > ..._...... I v E> f> v veee ee ' o -~ • ------f e e o o f-e~~ 1_1 Vf) o / f> e eo o 1 - .. e oOV e e • • • f> v -- "" A e I e I I 0 --- 't-' 0 e ee e e/ e • It> • 8 e e ' o---_fJ e e e e • I e eve e / -- o It e Ia_ e • e e I v o ' o ..o... __ 0 0 ' e ~e· ---:e.... d. • v 1 olV fe!£L______je -----J'J.JI~, • ~ o o " \f) - e 1 e e f) ( 1 • 0 f) • " e e I "e e e o o ;' e o ~~," le a• v o ~ ? teo o e~e o • e ~ o/ v, e o •• oV'V J • o e v _..e 1 e•• tt"\ €)---Q_..Q..o v .l ~ L 0 I ... __ ------, 1 e o Oi' ------,0\ e/t:> v e ----- I 0 V o9V ----- I : v o e ---1--L_ o e ---..o ------~~--~----_.----~----~----~----._----~----~----~----~----~----._----~----~-----L----~~~oBv o96 o86 o001 ol01 oVOI o901 o901 o01t olt1 oVt1 o91t o81t oOlt oll1 oVll o9l1 o8l1 <]

·sa~'B~S pa~JU fi SUOUJW.IalUOJ aq1 JO S{'BJ.Ia~'BW

o98 o'176 oll

SH3.l31r't1011>1 000 0 1 I r" t S3lllr'tl 000 0

,. e e e 1 ) • .I :\._...-----c. Cl ._J -I ._._-e:-\ ~ ,v u • ~ -- I ec.· )e o ' u e I o e e / e •\. o e e 0 eUUC)uU , e I u eu<, 1 ~ Jo eu ··\.._e .,., \ e e.{) r Cl Cl. ~-~e--.,~ Cl e o o•.... 0 e ' 1 \ • 1" ... ---" ... , '-- ef) • e' 1 ~ o u u e •"~~ eeu\s e ., ele_~.-£-~ • e • .~ e • €> '- U -.l----~ f I ' ..... -\ "" -~J'C I {) "'-'"- {" \ 0 e • e ~ .... u u e e u ~/e e e e • le v e {) ee e • _,.r Cl- e --.rc -c ---~e---'u e e • v ~ _!'---,....,....-~ .,~ e ... e e Iii------r .. r~ ' e ,...., e e --~ .1 e •e u e ~ \ e e 111 e e u e .... .r...-v( e •../'A ~ .... u e B e ' • e e I \ • ee • }" / L e e I J • ~ ...... \.,_...-,,.rJ e ~ e ~~ e !... ..,\~f.- fj/fl: ee ., fo'"' e ., ., \ e e 4 ., .,., • "'e.., • • • • ~-L- "'\~-~.,rue e l 1 e f\ " )};-----e e uV • lf e u • • { ------""j. __.~.ee ~ • le.,u., 1 e\ ...__ u 1 e le t• e e • e " ~· e e e oc~-.9 o e~e \ I . Cl ~ ~ ., -~ e ~~~~ e --- eu t- -., e~ > ... o \ .... _.--fJ ' e ~ ~ ...~,, e e e 0 e \.,_fL------~ ~c-~ e e v • e ~ ...... -~ o ., ., 1> ., e ;-,, e !" 1 ·\u e e "' • I u\ e'"' o e .., ., u ~ i o ,u ( \ ~ ', \ I ( {)/ • .. €> 'I €> f- L( e \ e / .g. ~ ~ ' o \ ~ e_:F--- e e c,--t. f) -{' e v ., y- [email protected]!~~., e €>'

.I e ' \ ( ~ ...... """.,--"'""-_ j ·e l 1,.-­ \ I \j \CI. ._.,"\) I

olL o98 o88 o06 ol6 o'176 o96 FIGURE 2.-Physiographic regions of the conterminous United States.

The logarithmic variance of fluorine concen­ the fluorine concentrations of the samples, ex­ trations in all 911 samples is 0.305, indicating that pressed in terms of five geometric ranges of con­ the analytical-error variance contributes less than centration. 37 percent to the total variance in the data. DISCUSSION

RESULTS OF ANALYSES Fluorine is widely distributed in nature, and is a Statistics for the fluorine concentration of all common constituent of most soils and rocks. Most samples, as well as of samples from both east and of the fluorine in soils is thought to be derived west of the 97th meridian, are given in table 2. from the geologic parent materials. Hawkes and Figure 3 shows the distribution of the sample sites Webb (1962, p. 365) gave the average fluorine con­ throughout the conterminous United States and tent (ppm) of rocks as follows: Ultramafic, 100; mafic, 370; felsic, 800; limestone, 51; sandstone, TABLE 2.-Concentrations of fluor-ine, in parts per million, in 290; and shale, 590. Kokuba (1956) reported the samples ofsoils and other surficial materials from the conter­ following ranges in fluorine content (ppm): 100-800 minous United States in 99 samples of volcanic rocks; 160-2,900 in 5 [Number of samples is given in parentheses after area] volcanic ashes; and 120-2,400 in 28 samples of plutonic rocks. This element is added to soils in Area many regions by atmospheric fallout from in­ dustrial activity, by volcanic ejecta, or by the application of phosphate and other fer­ Entire conterminous United States (911) ...... 10-3,680 180 3.57 400 tilizers containing slag. Western United States, west of the 97th The increasing importance of fluorine con­ meridian (491) ...... 10-1,900 250 2.66 410 Eastern United States, tamination of agricultural areas by industrial east of the 97th processes was emphasized in a report by the Ger­ meridian (420) ...... 10-3,680 115 4.38 340 man Research Society (Deutsche Forschungs­ 'Estimated by method of Sichel (1952). gemeinschaft, 1968, p. 1) as follows [translated]:

6 Fluorine damage has been known and examined for almost where sources of possible contamination were not 100 years. While earlier it was mostly single occurrences, today, obvious, fluorine contamination may have oc­ because of heavy industrialization of numerous districts, the areas have become very small where one can safely suspect no curred at some locations. For most elements con­ fluorine emissions. Meanwhile, we have learned that the source sidered in this study, particularly those that form of these emissions is by no means limited to the use of fluorine­ compounds of low solubility, we believe that the containing raw materials (fluorspar) but also includes metal­ depth at which the samples were collected working factories, hydrofluoric acid production, and precluded gross contamination. Robinson and enamelware factories, and that fluorine emissions also originate from electric power plants, brickworks, and so forth. Edgington (1946) reported that virgin soils contain One must further bear in mind that the emissions can be widely more fluoride with depth, but that with regular distributed by the wind and, also, that in nature soils with high fertilization soils had the greater fluoride concen­ fluorine contents occur, so that in a district with elevated trations near the surface. This observation agrees fluorine levels in forage plants, for example, far-reaching with the known low mobility of most fluorine com­ sources must be considered if the emissions are not always present in an easily recognizable form. The fluorine problem in pounds in soils. the German Republic is truly a general problem and not an oc­ Fluorine, like selenium, plays a dual role in casional local condition. animal nutrition-small amounts are essential, but larger amounts may be deleterious The high levels of fluorine in some soils may be (Underwood, 1971, p. 369-388). Animals may be attributed to volcanic activity. No soil sample adversely affected by eating forage plants that reported in this study is thought to have been in­ contain 50 ppm (dry-weight basis) or even less of fluenced by historic volcanism, although fluorine fluoride, although the plants may exhibit normal from ancient eruptions may remain in some of the growth (Brewer, 1966, p. 180). The importance of soils that were sampled. The effects of a recent adequate fluorine in food or water for bone and volcanic eruption on the fluorine content of sur­ tooth development in humans is well known, and ficial materials are illustrated by Thorarinsson's problems of excessive fluorine in (1970) report of the Mount Hekla, Iceland, eruption causing mottled teeth occur in local areas. of May 5-July 15, 1970, as follows: "The tephra production was considerable, totalling ap­ Although low concentrations of fluorine have 3 been reported by Nikolic (1956) and others to proximately 30 million m • * * * The area on land receiving more than 100 tons/km2 was about 9,500 stimulate growth in plants, this element is not con­ 2 sidered to be essential for plant growth (Brewer, km , or nearly one-tenth of the country. * * * The tephra proved unusually rich in fluorine (up to at 1966, p. 180), and high concentrations in the air or least 1,500 ppm) and caused lethal fluorine ­ soil are toxic to plants. Fluorine levels in soils that ing in the grazing livestock, especially sheep. The are injurious to plants are controlled more by soil situation is really very serious, especially in some type, calcium and content, and soil pH districts on the north coast where the tephra is than by total fluorine that is present because only very fine grained and washes out more slowly than the soluble fluorine is absorbed. Sandy acid soils expected. The new grass growing through this ash low in phosphorus favor the development of soluble is also poisonous." forms of fluorine. Fluorine concentrations in some samples of the The differences in fluorine concentrations in present study exceed that of the Iceland tephra, samples of surficial materials from Western, com­ but for the most part, this fluorine is probably pared with Eastern, United States (table 2) are fixed in relatively insoluble compounds. Soluble significant at the 99-percent level of confidence. fluorine compounds are almost completely fixed in The high levels in samples from the central and a soil of pH 6.5 or greater in the presence of ade­ north-central parts of the Cordilleran Mountain quate amounts of calcium carbonate (CaC03) region (figs. 2, 3), probably reflect the higher through the formation of relatively insoluble fluorine concentrations in the rock types from calcium fluoride (CaF2) (Brewer, 1966, p. 195). In which the soils were derived. Samples from the the absence of adequate calcium, the formation of Appalachian Highland region and the Ozark region aluminum silicofluoride, (Al2SiF6h, accounts for of Eastern United States (figs. 2, 3) tend to contain the observed fixation of the fluoride (Brewer, 1966, fluorine in concentrations that are greater than p. 183). average, which probably also resulted from the Although most of the samples of surficial higher fluorine content of the parent rocks. In con-· materials collected for this study were from sites trast, the surficial materials from the Atlantic

7 8

fUP!JJns u! suo!l'BJluaauoa au!Jonu-·s ~anm.!J

olll oVH o9n

L!n: 'uo11e!AaP l!Jlawoa9 -1 0 ll 081 'ueaw l!Jlawoa9 NOilliW 1:13d Sll:l'lfd Nl '3NII:IOnl:l ~wN- o"~\ gggggggg~~Ci~ oVl 0\. l ~ 0!1 ) () \ eo o. o9l e e \ ... 001 v o e e e ~~- ... .J "'--,, e e e l .. \ 0!11 o8l e ev • e ', e o e cf'Jv e• ·~ ooz e e e e e e e., p-L-.!_!_Q"- r-r~ , .. ., .. 0 •• ., ..... !. ., .. -, ., -- I.. .. ,, I HI I e e/a e ' I I I I oO£ ~-"""~p"" ,._,_e e b e • e• e e 1I • e .,...... , , I •;; ~vi~ ... ~ oc;; Lo!lz e ,_f e • e p • e e , S3ldwvs w1o1 :~o 0 () CJ • • CJ () CJ CJ • • ON'If 108WAS e 1 e ~ -~'lflN3::11:13d • ~ e I • 1 ol£ I e • b e • • e ._ e.- ee oo ee~ • e I e e e e / ' • ,.1 e e l el e e I e \ ~----..tl ~ e • e., 1 • o e • o_i_o_c;--e--r~--L • .. •.,:/ • • ,"-. o • oV£ e ~ e --__._ ~ e 1 • I ~ e e e • • • J v • • --4-..o.___ e r •• Jo ' , • e• .,I ----el•., \ ~lie e I e I ' e I o9£ e ., ' • e 1• I • • \ ....' -L---~-!_! -l• I• • e • •e I • I .-,..... • ].,.. •• • .. I • I •• ~ ·~ e e!..~.•T .._ -- e•e e•~ e•e • • ee ' ~ e o8£ \ o o v o e ee ~ • e --€" - __... .,. • ~'1 \ ee f> •• ~ • A. e e e e 1flL ., • f>e 1 > ...... __,...... __ ~ e f' ~ 'e• .... • 1 o --S • ------~e • .,e • • /--!_• .L_' ee., • I o .,, .tl • e e 1 e - -- • w f> oOv ,e e • T • e I e ., e --- , e o I e -. e • ere e A • ~ • e • t' ~---I: ., I e 0 e I I Cl •• e CJ -...e.._ ' e i-!L- _.___ • e ., , • e e 1I -- 0 -~- jl - a---- •J.....e,. • e e; • e e olV e ------J • ., • 'e -., 1 • e e ( ' • e e1f e 11 , e 1 e t~e 11 • • I • • • le e • • • ~ ....~ (I •.,e e \v e 8 • e e • ,' • " • e oVV .\_ e e I> I> fiiJI> I "ee \ .,, eJ---!_L.tt~ 1 ·------L ~·/1 I e .,.. e .,,I ------\ .,,. e \.e ---- I Cl Cl ---- 1 : e e v ----L~L_ e e --~...

o96 o86 oOOI ol01 oVOI o90I o80I o011 olll oVll o911 o811 oOli olli oVli o9li o8li 6

·sawlS pal!Ufl snou!w.Iawoo aql JO S{'B!.Ial'BW


SH313W01DI OOS 0 I I I I r I S311W 009 0

0 .... ~ e•e 0 0 I ~_'1\Ni"\"fll".) e I ..._-~ ~ 1 ee" ,'o ej o e e o • o \. o o e 0 j'- 1 e - ~· 1 ~ J o e •,'; 0 \> 0 0 • e rl e e e ~-e-v--o !e e e e 0 v \ ( !::""""' o ... e•o e v' I l e I ...... -""' ~ 1 o o o , e e e~ e!1 1 0 , e c-~ _l-~!>-!1'-~~)-' e e e e 1 e e · '--\ 0 /~TJii"" I o e "'--- ,~ o eC..-6"' • o L. \ 0 cVOV e e _,./- e e e e e -c•r!__t_c_e f2..J2_~V e e eo ____ ~---/--c--o-e __o @t.«:'..,.re- e.e0 e • ~ o ,ti.--- 0 ---C" f v c v e -~- ' F o i e o,J....-./... ~ ,..,.;,\ \.._ ·~ e e :e ~ ~ o I \ • v f"' c e 'J e I o • • " 1 , e v .J, e I/'-\.,_,.. -, ....fJ \ e """ I e e I e e ., •' • >e ' ~ - I< ,:J "'· ., ,.C> e e • • \ ., ., ..1 ., e ., e._ ., ., ., .,~ )_ a ""\~ ~( ?e ,., f) I ~-~- _,.y---\.(1"' - ...>----c • e'V' e e e • ~ 1 e e ( " ------\' /e•• ? vo~ le e--. ' e I \_ e ~ e -' •' ( • ~ ., o ., ., • c~- • ., /.,., ., ., ., o \ ., -..L... c e - e -~• I ;re- C> .,., '>-- ·-:-u -~-ii--e ., ., , e_ ( -~..\e • e e are------,\1 ~____,-~ <> ., o -"- • ., e le ~ .., ~ • 1 ·•'"' • o 'J e I \0 '-1"1\ \1 e; ee><>@I) v 1 1 C> \i •'.~-!./ 7 0 C> f'-1 C> e'~ ~- -f f) <> e Cl ( e\~ \ ~ ... --"'V''1_...... __ i ,. I I r-­ \ I \..i \~_,-J

o06 oV6 o96 Coastal Plain (fig. 2) that largely originated from occurs as a soil contaminant resulting from old highly weathered marine deposits tend to con­ agricultural practices may be absorbed by plants. tain fluorine in low concentrations. Individual Liebig (1966, p. 14) stated, "Crops grown on sampling sites within this region where the soils arsenic-contaminated soils contain more arsenic in contain exceptionally high fluorine concentrations the tops and roots than crops grown on unsprayed may reflect industrial contamination. One site in soils, but large amounts of these crops would have central Florida that had high fluorine levels was had to be consumed before toxicity to humans or associated with phosphate deposits, and the one animals resulted." site in western Kentucky having a high fluorine Arsenic enrichment of the upper horizons of soil value was near a fluorspar mine. by means of plant transport and deposition of arsenic obtained from lower horizons probably is ARSENIC insignificant. Williams and Whetstone (1940, p. 12) ANALYTICAL METHOD reported that arsenic concentrations in native Arsenic concentrations in the samples were plants that grew on uncontaminated soils did not determined by an evolution­ exceed 10 ppm in dry plant material and that most spectrophotometric- dilution method samples contained less than 1 to 2 ppm. Liebig (Claude Huffman and J. I. Dinnin, U.S. Geological (1966, p. 13) stated, "Apparently, the effect of Survey, unpub. data, 1973). The logarithmic arsenic toxicity is such that plant growth is limited variance of this method was found to be 0.033. This before large amounts of arsenic are absorbed and means that the analyses are reproducible within a translocated to the top." factor of 1.52, computed as the antilog of sa at the TABLE 3.-Concentrations of arsenic, in parts per million, in 65-percent level of confidence, or within a factor of samples of soils and other surficial materialsfrorn the conter­ 2.30, computed as the square of the antilog sa at ·minous United States the 95-percent level. The logarithmic variance of [Number of samples is given in parentheses after area] arsenic concentrations in all 910 samples is 0.093, indicating that the analytical-error variance con­ tributes less than 36 percent to the total variance Area in the data. RESULTS OF ANALYSES Entire conterminous United States (910) 1-97 5.8 2.02 7.4 Western United States, Statistics for the arsenic concentration of all west of the 97th samples, as well as of samples from both east and meridian ( 490) ...... 1.2-97 6.1 1.82 7.2 Eastern United States, west of the 97th meridian, are given in table 3. east of the 97th Shown in figure 4 are the distribution of the sam­ meridian (420)...... 1-73 5.4 2.24 7.5 ple sites throughout the conterminous United 1Estimated by method of Sichel (1952). States and the arsenic concentrations of the samples, expressed in terms of five geometric Although the beneficial effects of certain organic ranges of concentration. compounds on the growth, health, and feed efficiency of poultry and pigs have been well DISCUSSION established (Underwood, 1971, p. 427), most in­ Arsenic in measurable concentrations is a organic compounds are highly toxic to animals. common constituent of rocks, soils, waters, and Average arsenic concentrations (ppm) in rocks plants. This element is not considered to be essen­ were given by Hawkes and Webb (1962, p. 360) as tial for either plants or animals, and some arsenic follows: Ultramafic, 2.8; mafic, 2; felsic, 1.5; shale, compounds are extremely toxic to both. Relatively 4; and black shale, 75-225. Arsenic concentrations small amounts of arsenic are absorbed by most in samples of soil from 12 great soil groups, as plants from soils that have natural arsenic concen­ reported by Williams and Whetstone (1940, p. 6- trations. However, the arsenic levels in Douglas-fir 10), ranged from 0.2 to 41 ppm, with podzol soils stems have been used successfully in prospecting having the lower range of values and the prairie for ore deposits (Warren, Delavault, and Barakso, and chestnut soils tending to fall in the upper 1968), and arsenic solubilization in the humus range. Headden (1910, p. 349), in an early report on layer of some soils was attributed to plant action arsenic in · virgin prairie soils from Kansas and by Hawkes and Webb (1962, p. 360). Arsenic that Colorado, stated, "I have examined virgin soils, all

10 of them marly, from localities many miles apart, Mobility of arsenic in soils is generally low and have found them to contain arsenic, calculated because of coprecipitation as As03;) with limonite as , as follows: 2.51, 2. 76, 2.8, 3.8, 3.99, and as FeAs04 (scorodite) (Hawkes and Webb, 4.2, 4.7, and 5.0 parts per million of soil [range, ex­ 1962, p. 360); nevertheless, arsenic from surficial pressed as arsenic, 1.3-2.5 ppm]. These quantities contamination has been reported to move down to cannot be considered as mere traces, but are quite depths of 2-3 feet (60-90 em) in irrigated orchards, small compared with the arsenic found to have ac­ although most of the arsenic remains in the upper cumulated in our orchard soils, which show an 12 inches (30 em) of soil (Dr. N. R. Benson, oral average of 47.7 parts arsenic acid per million." commun., May 12, 1971). The loss of arsenic from Arsenic contamination resulting from soils is thought to result from leaching and agricultural practices and industrial operations is through conversion of arsenical compounds to· ar­ widespread. and paris sine (AsH3) by the action of soil fungi (Williams ( and acetate) were widely and Whetstone, 1940, p. 3-4). used as on vegetables, fruits, and field We do not know the extent of arsenic contamina­ crops from early in this century until they were tion of the soil samples used in this study. The almost completely replaced by chlorinated selection of rural sites, the avoidance of cultivated hydrocarbon insecticides around 1945-50. Apple soils where possible, and the depth at which the orchards commonly received lead arsenate at the soils were sampled probably prevented a signifi­ rate of 2 pounds per acre (2.2 kg/ ha) in each spray­ cant amount of contamination of the soil samples. ing, and the trees were sprayed 7-8 times per year The estimated arithmetic mean of these samples, (Dr. N. R. Benson, oral commun., May 12, 1971). 7.4 ppm (table 3), is somewhat greater than the Benson (1953, p. 215) wrote, "Almost all land that mean of 5 ppm given by Hawkes and Webb (1962, has been used for the commercial production of p. 360) and is more than twice the highest value apples or in eastern Washington contains found by Headden (1910, p. 349) in virgin prairie enough residual lead arsenate from insecticidal soils. The range in values in this report is con­ sprays to interfere with the growth of most plants. siderably greater than is commonly reported for Keaton (1937) has shown that the unproduc­ soils that are presumed to be uncontaminated; the tiveness of these soils is associated with arsenic highest values approach those of total arsenic at residue and not with the lead residue." Arsenical the lowest level classified as toxic by Benson (1953, compounds (principally sodium and p. 221). However, the toxicity of soils to plants arsenic trioxide) were widely used as depends on the available arsenic (commonly ex­ until replaced by synthetic auxins at about the pressed as soluble or extractable arsenic), and we same time that the use of arsenical insecticides have no measure of the arsenic present in this was discontinued. form. Hawkes and Webb (1962, p. 360) reported, "The The mean arsenic concentrations in soils from As content of ash is extremely high. As a the Eastern and Western United States are similar result, burning of coal releases As to the air and (table 3). The most pronounced pattern in concen­ causes contamination of surficial material tration (fig. 4) is that of low concentrations in throughout the surrounding country." The concen­ many samples from the eastern and southern parts trations of arsenic in soils that were attributed to of the Atlantic Coastal Plain region (fig. 2). smelter in the Helena Valley, Mont., area Clusters of high values appear in the central part where reported by Miesch and Huffman (1972, p. of the Cordilleran Mountain region, the Ozark 74) to decrease with distance of the sampling site region, and parts of the Appalachian Highland from the smelter stack and with the depth at which region that may reflect the arsenic content of the the samples were collected. Expected concen­ parent geologic materials. trations of arsenic in the surface layer (0-1 inch; 0- REFERENCES CITED 2.5 em) of soil ranged from 140 ppm at a distance of Allaway, W. H., 1969, Control of the environmental levels of 1 mile (1.6 km) to 4 ppm at a distance of 4 miles (6.4 selenium, in Hemphill, D. D., ed., Trace substances in en­ km). Soil from a depth of 6-10 inches (15-25 em) vironmental health-II: Missouri Univ. Proc. 2d Ann. Conf. on Trace Substances in Environmental Health, p. 181-206. ranged from 13 ppm arsenic content 1 mile (1.6 km) Anderson, M.S., Lakin, H. W., Beeson, K. C., Smith, F. F., and from the stack to 5 ppm 4 miles (6.4 km) from the Thacker, Edward, 1961, Selenium in agriculture: U.S. Dept. stack. Agriculture, Agriculture Handb. no. 200, 65 p.

11 61

J'B!J!JJnS U! SUO!l'BJlUa;moJ J!UaSJV-"f' :rn:nDI.tJ

zo·z "UO!li!!I\8P 3!Jl8W08!) oll 8"5 'ueaw JUlaWDa!) NOilliW 1!3d Sli!Vd Nl ':JIN3SI!V =~~~NN-- A WCO-•OOCOQU'1-COa.I~W...... ,_. __ _ N:-Nc:...eau.u,u,w:.....u,a,u,:,:.. ~~ oVl


) {)'l I I .._,e ', I ~II o9l e o ~ _ I I DOL (] C ' ' I ' ~ '- I I 05L ., e ., • \ 1 1 9 Looz '!;~-~~ ~., o8l e • • v .. • \. I ~ cac ~ """' e e v • ••• - • 101' c ., e oe .,-L..tl_!<_fZl--- e .,'\. r-r:-u-o,,....._I e c o '- '"""''"""""",. ••• oaoAs0 ~ 1 c v 0 b • v .,v v e ~L.. e v ...... _, ' oOE cec.,e e e e e ., ' ., ee ., •c' ., o e a.L--~ ., c • ,., • o ., f • e ' • ':. c ,oI e • ., ., e• o ",.e ce eeo er\ .. e ., e - .--~."'t>~ ~ ,_..,1 e e c • e. , - olE C flflee I .,.• fl!fl~ e e e., '1 e •• e~I o • I e ., 1' ., ., • • !' v o eJ e o o, • ., .,e • e.,.. ., r-., '\ oPE e v v 0 ._ ___ ;fj_!_!L_~~-...!.-L.Q.. _____ !__•,je 0e\ •. --e------Too e ., o v / e 11 e • \ • • e e e .I ., e I V, • e c e e 1 ., c I• e I/ '! o9£ 0 e e I.1 0 I· I • • \ (] I c ., ., I e I e, e) e ., ., ., c • ...__ adI eev 1e • ., • e, ve ~~-l fl ~flee fl·"'e I .. e e I fl !._~----- ~ o8E ..' - ,. e e • ., e:...~vT.zc.v ~ ___ "'¥"_ L--, • e·~ e 8"'• o .,~.... ee• • e / e., • e f.,e ., e e e • ,. "., •/ o ., ~' o o o ., o ., "'., ., 1---e-L..1 ____ ~ • .. o oOv 1 F., vee., • e ., • 1 ee ., e ., ., 1 , .-----...re ao ' 'i'-.....~------1o ~ e o I e ., ., / --~-- -;~ I'e •., e .,,.,t e eoc e ., ., ,I "e e e e., ., ef I ., e• e ., e e • o e _.~ I • .,. e l£l ___, ______e ... J J o'1 ' I ., 0 v olV f 0 1 v J•• .,e e e ,'? o ,1 fl o e '" •., ' ------• ' .. 0 0 "' I • ' (] ,.-,~ .... -""'----e e I e., e •e• fl ~-----'""'- ~,f>, .,'e e e e • I e •e• • e e• ...... , , 1I ., e : oVV ej o II '"ioe •f• e .. 10 .. • c elf). I ~I I 0(] 0 • ' ve l I ' 0 v __ .\.______I ------1 --L_ ---.Q____ _ o9V

o96 o86 oOO! olO! oVO'I o90! o80! oOH olH oVH o9H 8H oOl! oll! oVl'I o9l! o8l! f!l

·sa~\1~8 pa~JUfi SOOUJW.Ia~UO;> aq~ JO Sll1J.Ia~\1W

oV6 o96

S~3.L3V1101Dt oog 0 I I, r' f S311V11 oog 0


~~{) 01 -~~~~r -~-Af ~ u ... '1 .., ~ o e) e e • / v c • \.1 o o e 0 0 O~ I t J 0 ·- \() 0 ') {) \ o 0 ~ o v e le e • e 1-e___ c -.e v \ 1 'r Co~ee ev--~ 0 o0 0 V\ \ I ~\ e ...,...._I ...... _.,..," COV, oe I , ., o-)o ~..!..-.,-~o_ _!~_. • e • ~ • e ..... -\ {) /-i'\1'""U 1 e I e e -4--- '-t' ( , 0 o e c.-1' v e _?J... o..- • • e e c • v ~?• c ~ c • \• e v ., o ~---_!(___ ,..,..--oo;--e--e~-c.e .-.-;; o-e~ ---e / c o e..r-- \ v r..--.-- o ....-...; • o c -~ ' ev ,_, v v,.r "\ e •1..:..""'~ ~ .... v o v v :e • e v o e o• " • I J o o I ./1 • ~--..\.,.._,.._ J !..,. ee ~ J 1 ._r \ {) I I ... ~t e e e•' --< e ,., , ~ \ ...... ~~./'~e,~e e • e\., • e\ e e•e eo_e • e •~•-• .~->-~\ ::----->""'--• • • l e • • • \ ' v ~ ------~...., -- ve• llle v t • ( ,. C e {) I e ee C I ., - e [.I> • • e e ' - 1 • e o <>.fl \ ., ..\..I " --~--•- •e -- .,e ,.--e____..:..e e..,.r "-,_ e Cl -. e oe ,e~--- ~( !....-.-~ o e • e ., o ~ .,-. "' \ \ o o 00 oe ~ • 1 , o '~ 0', ., ., ~..... • v I 1 I 'I> 0 I • \ ( e\~~--- ~ o' J 0 o f' • c~>-.o-r ·r o o I - / 0 .I ( ~1 • / _ e I I ~'...... I \c -J' -._,...__ \.[-- J .,, I )

o96 Beeson, K. C., 1961, Occurrence and significance of selenium in Helena Valley, Montana, area environmental pollution plants, in Anderson, M. S., Lakin, H. W., Beeson, K. C., study: U.S. Environmental Protection Agency, Office of Smith, F. F., and Thacker, Edward, Selenium in Air Programs Pub. AP-91, p. 65-80. agriculture: U.S. Dept. Agriculture, Agriculture Handb. Muth, 0. H., and Allaway, W. H., 1963, The relationship of no. 200, p. 34-40. white muscle disease to the distribution of naturally oc­ Benson, N. R., 1953, Effects of season, phosphate, and acidity on curring selenium: Jour. Veterinary Med. Assoc., v. 142, no. plant growth in arsenic-toxic soils: Soil Sci., v. 76, no. 3, p. 12, p. 1379-1384. 215-224. Nikolic, S., 1956, Contribution al'etude de l'action du , du Brewer, R. F., 1966, Fluorine, chap. 12, in Chapman, H. D., ed., et du fluor dans Ia nutrition des plantes et dans la Diagnostic criteria for plants and soils: Riverside, Califor­ fertilisation [Contribution to the study of the action of nia Univ., Div. Agric. Sci., p. 180-196. nickel, cobalt, and fluorine in the nutrition and fertilization Cannon, H. L., 1960, The development of botanical methods of of plants], in Centre Internat. Engrais Chim., 5eme prospecting for uranium deposits on the Colorado Plateau: Assemblee Gen., 1956 (Beograd) Rappt.: v. 1, p. 195-218. U.S. Geol. Survey Bull. 1030-M, p. 399-516. Oldfield, J. E., 1972, Selenium deficiency in soils and its effect Deutsche Forschungsgemeinschaft, 1968, Fluor-Wirkungen: on animal health: Geol. Soc. America Bull., v. 83, p. 173- Forschungsergebnisse bei Pflanze und Tier [Effects of 180. fluorine: Results of research with plants and animals]: Robinson, W. 0., and Edgington, G. 1946, Fluorine in soils: Soil Wiesbaden, Forschungsberichte 14, Franz Steiner Verlag, Sci., v. 61, p. 341-353. 149 p. Shacklette, H. T., Boerngen, J. G., Cahill, J. R., and Rahill, R. Frost, D. V., 1972, The two faces of selenium-Can selenophobia L., 1973, in surficial materials of the conterminous be cured?: Critical Reviews in Toxicology, v. 1, no. 4, p. 467- United States and partial data on cadmium: U.S. Geol. 514 (published by The Chemical Rubber Co.). Survey Circular 673, 8 p. Ganje, T. J., 1966, Selenium, chap. 25, in Chapman, H. D., ed., Shacklette, H. T., Boerngen, J. G., and Turner, R. L., 1971, Mer­ Diagnostic criteria for plants and soils: Riverside, Califor­ cury in the environment-Surficial materials of the conter­ nia Univ., Div. Agric. Sci., p. 394-404. minous United States: U.S. Geol. Survey Circular 644, 5 p. Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon Shacklette, H. T., Hamilton, J. C., Boerngen, J. G., and Bowles, Press, 730 p. J. M., 1971, Elemental composition of surficial materials in Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in the conterminous United States: U.S. Geol. Survey Prof. exploration: New York, N.Y., and Evanston, Ill., Harper & Paper 574-D, 71 p. Row, Publishers, 415 p. Sichel, H. S., 1952, New methods in the statistical evaluation of Headden, W. P., 1910, The occurrence of arsenic in soils, plants, mine sampling data: London, Inst. Mining and fruits and animals: Colorado Sci. Soc. Proc., v. 9, p. 345-360. Trans., v. 61, p. 261-288. Ingram, B. L., 1970, Determination of fluoride in silicate rocks Swaine, D. J., 1955, The trace-element content of soils: England, without separation of aluminum, using a specific ion elec­ Commonwealth Agric. Bur., Commonwealth Bur. Soil Sci. trode: Anal. Chem., v. 42, no. 14, p. 1825-1827. Tech. Commun. 48, 157 p. Keaton, C. M.,1937, Influence of lead compounds on the growth Thorarinsson, Sigurdur, 1970, The "Hekla Fires''-A of barley: Soil Sci., v. 43, p. 401-411. preliminary report of the 1970 Mt. Hekla volcanic eruption: Kokuba, N., 1956, Fluorine in rocks: Faculty Sci. Kyushu Univ. Washington, Smithsonian Institution Center for Short­ Memoirs, ser. C, v. 2, p. 95-149. lived Phenomena, 2 p. Lakin, H. W., 1961, Geochemstry of selenium in relation to Underwood, E. J., 1971, Trace elements in human and animal agriculture, in Anderson, M. S., Lakin, H. W., Beeson, K. nutrition [3d ed.]: New York and London, Academic Press, C., Smith, F. F., and Thacker, Edward, Selenium in 543 p. agriculture: U.S. Dept. Agriculture, Agriculture Handb. Vinogradov, A. P.,1959, The geochemistry of rare and dispersed No. 200, 65 p. chemical elements in soils [2d ed.]: New York, Consultants ___1972, Selenium accumulation in soils and its absorption Bur. Enterprises, 209 p. by plants and animals: Geol. Soc. America Bull., v. 83, p. Warren, H. V., Delavault, R. E., and Barakso, J., 1968, The 181-190. arsenic content of Douglas-fir as a guide to some , Liebig, G. F., Jr., 1966, Arsenic, chap. 2, in Chapman, H. D., ed., silver, and base metal deposits: Canadian Mining and Diagnostic criteria for plants and soils: Riverside, Califor­ Metallurgical Bull., July, 1968, p. 860-866. nia Univ., Div. Agric. Sci., p. 13-23. Williams, K. T., and Whetstone, R. R., 1940, Arsenic distribu­ Miesch, A. T., and Huffman, Claude, Jr., 1972, Abundance and tion in soils and its presence in certain plants: U.S. Dept. distribution of lead, zinc, cadmium, and arsenic in soils, in Agriculture Tech. Bull. 732, 20 p.

:, u.s. GOVERNMENT PRINTING OFFICE: 1974-543-583/ 11'2